A radial adjustment of a tool cutting edge has basically two different areas of application:
(a) a compensating for the wear of a tool used in the manufacture of internal cylindrical surfaces, with the relatively small radial adjustment of the cutting edge occurring preferably when the tool is disengaged from the workpiece;
(b) a radial adjustment for the purpose of facing, taper turning or similar working processes, with the radial adjustment occurring during an engagement of the tool with the workpiece.
Devices in which the tool edge is adjusted by adjusting for a certain amount an adjusting ring provided with a scale, when the work spindle is at rest are already known. In order to obtain a continuous tool adjustment during the working process, the adjusting ring is connected to a fixed point of the spindle housing through a separate linkage, so that it does not participate in the spindle rotation, such that the cross slide is adjusted in dependency from the spindle rotation through the transmission gear (for example universal facing and boring heads of the Firm Wohlhaupter). A disadvantage of the devices known up to now is that they cannot be integrated into an automatic working sequence, since the adjustment or the coupling of the adjusting ring with the spindle housing must occur manually
Also a device in which the adjusting ring can be held by a separate locking mechanism constructed on the machine, so that also an automatic adjustment is possible (EP-A-O 155 241), is already known. The locking mechanism is arranged radially outside of the tool part on which the adjusting ring is arranged The locking mechanism considerably increases the entire space taken up by the tool arrangement and must be taken into consideration, for example, during an examination of a possible collision between the tool and the workpiece A further disadvantage of the known tool arrangement is that when the locking mechanism disengages from the adjusting ring, there is no longer any lock against an unintended adjusting of the adjusting ring. If, for example, the adjusting ring rotating with the entire tool should accidentally for example come into contact with the workpiece, there exists the danger that this radially adjusts the cutting edge.
The purpose of the present invention is to provide a device for facilitating a radial adjustment, which device facilitates an automatic radial adjustment of the tool cutting edge both for the purpose of facing, taper turning or comparable operations, which device has an effective lock against an unintended radial adjustment of the tool edge, and which device has a simple, compact design.
This purpose is inventively attained by providing a locking mechanism which is, in contrast to the construction described in EP-A-O 155 241 which is not arranged stationarily radially outside of the tool, but is constructed as a retractible and extendible locking ram on the spindle housing. The locking ram can during the time which a radial adjustment is not demanded, be completely retracted, so that it cannot be in this respect a collision obstacle for example with the workpiece. The locking ram lockingly engages in its extended position the adjusting ring, so that the rotary movement of the spindle can then be utilized to carry out the radial adjustment of the tool cutting edge. The locking ram has at the same time the task of operating a locking member, which in a locking position locks the adjusting ring against rotation, however, in an unlocking position releases the adjusting ring.
A further development of the invention supports the locking ram for movement parallel with respect to the direction of the spindle axis. It can thus be arranged substantially within the peripheral contour of the tool, so that this measure contributes to the locking mechanism, even in the extended condition, not creating any collision problems.
The locking member is constructed in a further development of the invention as a bolt movable parallel with respect to the direction of the spindle axis and supported fixed against rotation in a recess of the adjusting ring. The bolt engages, in its locking position by means of a tooth system constructed on its periphery, a tooth system connected to the tool-carrier housing. Depending on the chosen size of the tooth system, a more or less finely tuned radial adjusting and fixing of the cutting edge is possible, as will be described in greater detail later on. Other possibilities of the locking engagement between the locking member and the tool-carrier housing are for example the Hirth-type serrations, the perforated disk and locking bolt or mechanical, hydraulic or other couplings.
One exemplary embodiment of the invention provides a transmission gear having an adjusting thread constructed in the inside of the adjusting ring and arranged coaxially with respect to the direction of the spindle axis. The adjusting thread cooperates with a counterthread provided on an adjusting piston supported for axial movement in the tool-carrier housing, such that upon rotation of the adjusting ring relative to the housing, the adjusting piston is moved, and that an extension inclined with respect to the direction of the spindle axis is arranged at the end of the adjusting piston facing the carriage. The extension is received snugly in a recess constructed on the carriage. Thus, an axial movement of the inclined extension with the adjusting piston results in a forced radial movement of the carriage. This construction is preferably intended for a tool in which a radial adjustment is carried out only for the purpose of compensating for wear, and requires only relatively small radial paths of adjustment.
The transmission gear in another exemplary embodiment of the invention includes a gear drivingly connected to the adjusting ring, which gear cooperates with a rack connected to the carriage. This construction is suited for greater radial paths of adjustment, as they are needed for example during facing, taper turning, etc.
The locking ram is in a further development of the invention connected to a slide drive, which in turn can be controlled and automatically operated by a machine control.
A further development of the invention provides a counter for counting the spindle rotations or spindle angle of rotations. A computer is also provided for converting the spindle rotations which occur into a corresponding radial path of adjustment of the cutting edge. Counter and computer can preferably be integrated into the general machine control.